This project deals with both laboratory and clinical aspects of strongyloidiasis; the former with analysis and characterization of parasite antigens and immune response to them, and the latter with investigations of patients infected with this parasite. The parasite is itself unique because of certain biologic properties (such as absence of a parasitic male worm, free-living stage and internal auto-infection) and because of the fact that it can produce a serious, even fatal disease in certain immunosuppressive states. Since we have experienced problems in purification of the larval protease, attention will be focused upon other antigens that can be identified which react with IgE in pooled patients' serum. A cDNA library has been prepared from 3rd stage larvae of S. stercoralis, and several clones have been identified. Clinical studies, except for providing laboratory assistance in diagnosis of suspect cases, have been focused upon examining the IL-4 and IL-5 cytokine responses of selected cases to mitogenic and antigenic stimuli in vitro. The code has not yet been broken to see the results of a comparative treatment trial of strongyloidiasis with Thiabendazole vs. Ivermectin. This was carried out in collaboration with investigators in Lowell, Massachusetts, on Cambodian refugees found infected with the parasite.